1. Field of the invention
This invention relates to a gel medium for electrophoresis advantageously employable for electrophoresis of biopolymers such as proteins and nucleic acids, and more particularly to an aqueous gel medium for electrophoresis improved in physical properties.
2. Description of prior arts
The electrophoresis can be carried out in the following manner: a membrane medium for electrophoresis prepared by coating or casting a membrane-forming material such as agar, cellulose, cellulose acetate, starch, silica gel or polyacrylamide gel over a support such as glass plate or transparent plastic film is impregnated with a buffer solution or immersed in a buffer solution; on the medium is applied a substance to be analyzed (sample); the applied sample is developed (or resolved) on or in the medium by applying a voltage to both ends of the support and dyed; and then the dyed sample is measured on the optical density to quantitatively determine the components of the sample.
Details of the electrophoresis and medium therefor are given in "Experimental Text for Electrophoresis (5th revision)" editted by Electrophoresis Society of Japan (Bunkodo, 1975), "Modern Electrophoresis" editted by Aoki and Nagai (Hirokawa Shoten, 1973), etc.
Recently, the electrophoresis has been applied to analyze substances originating from a living body; for instance, the electrophoresis has been employed for analyses of proteins originating from a living body to be performed in the course of biochemical analysis for diagnosis, and further employed for analyses of fragments of DNA (deoxyribonucleic acid) to be performed for study of hereditary disease. Thus, the electrophoresis is now widely utilized, and the tests utilizing the electrophoresis are acquiring a greater importance.
As the membrane or sheet for electrophoresis, a filter paper was previously employed, but recently an agarose membrane or a polyacrylamide gel membrane has been employed in view of the properties. Particularly, the polyacrylamide gel membrane showing molecular sieve function is mostly employed at the present time. The polyacrylamide gel membrane can be prepared by crosslinking polymerization of a monomer such as acrylamide and a two-functional crosslinking agent such as N,N'-methylenebisacrylamide under oxygen-free conditions in the presence of water and a polymerization catalyst.
However, the conventional polyacrylamide gel membrane has a serious disadvantage in the membrane properties that the membrane is brittle and easily breakable. For this reason, a polyacrylamide gel membrane is generally prepared by a process involving: introducing an aqueous solution (gel-forming solution or gel solution) containing acrylamide, a crosslinking agent and a polymerization catalyst into a cell formed with spacers having a certain thickness (e.g., 0.3-1 mm) which are provided on a glass plate; covering the introduced gel solution with a glass plate for sealing the gel solution from oxygen; and causing the crosslinking polymerization to prepare the desired gel membrane.
Generally, electrophoresis using a polyacrylamide gel membrane should be provided with slots (caves) for receiving a sample. The conventional gel membrane, however, is very brittle and easily breakable, and accordingly the prepared gel membrane can hardly be subjected to cutting procedure by means of a razor for the purpose of forming the sample slots. For this reason, the sample slots are generally prepared by inserting a sample slot former into a gel-forming solution in advance of performing the gelation reaction. A variety of sample slot formers are known. For instance, a glass plate provided with projections for the formation of sample slots is generally employed in the glass plate-sealing method. The necessity of such additional operation is an obstacle to manufacturing the polyacrylamide gel in a mass scale.
The prepared polyacrylamide gel is horizontally or vertically placed for performing slab electrophoresis. The electrophoresis is performed for a certain period of time under given conditions, and the desired analysis of the components originating from the living body is done after dyeing the electrophoresed gel membrane with Ponceau 3R (Ciba-Geigy), Coomassie Brilliant Blue G-250 (ICI), silver, etc.